Domus Aurea

In 64 AD, Emperor Nero built a palace almost a mile long, stretching from Palatine Hill to Oppio Hill. Some of the pieces were covered with gold and precious stones and were beautifully decorated. After Nero's death, it was covered with earth to erase the memory of the tyrant. It was accidentally rediscovered in the 15th century, and today you can stroll through 30 of Nero's 150 underground rooms.